Line converter for coupling standing waves to a shield area of a three dimensional waveguide

ABSTRACT

A line converter includes ground conductors, a transmission-line conductor and a coupling-line conductor disposed on a dielectric substrate. A dielectric-filled waveguide includes a lower conductor plate, an upper conductor plate, a lower dielectric strip, and an upper dielectric strip, where the dielectric substrate is sandwiched between the lower conductor plate and the lower dielectric strip, and the upper conductor plate and the upper conductor strip, so that a conductor portion S that is part of the ground conductors of the dielectric substrate defines a shield area of the dielectric-filled waveguide. The coupling-line conductor is coupled to a standing wave generated by the shield area, at a position where the electric-field intensity of the standing wave is high. Subsequently, a plane circuit can be arranged so as to be substantially parallel to the direction in which an electromagnetic wave propagates through the three-dimensional waveguide. Further, the dielectric substrate can be easily machined and the characteristic of coupling between the plane circuit and the three-dimensional waveguide provided on the dielectric substrate is prevented from being affected by the precision of assembling the plane circuit and the three-dimensional waveguide so that a line-conversion characteristic according to a predetermined design can be easily obtained.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a line converter for a transmissionline used for at least one of a microwave band and a millimeter-waveband, for example, a high-frequency module including the line converter,and a communication device.

2. Description of the Related Art

In the past, line converters for performing line conversion between aplane circuit including a dielectric substrate and a three-dimensionalwaveguide for propagating an electromagnetic wave in a three-dimensionalspace have been disclosed in Patent Document 1 (Japanese UnexaminedPatent Application Publication No. 60-192401) and Patent Document 2(Japanese Unexamined Patent Application Publication No. 2001-111310).

In the line converter according to Patent Document 1, an end of amicro-strip line formed as part of the plane circuit is inserted in aterminal short-circuit waveguide tube divided into two parts by a planeE of the waveguide tube. The two parts of the terminal short-circuitwaveguide tube penetrate a groove formed in the dielectric substrate andsandwich the dielectric substrate therebetween.

In the line converter according to Patent Document 2, the dielectricsubstrate is provided at a position that is spaced away from ashort-circuit plane of a terminal short-circuit waveguide tube by asmuch as a predetermined distance and in a predetermined direction thatis perpendicular to the electromagnetic-wave propagation direction.

In the case of the line converter of Patent Document 1, there is a needto form a penetrating groove in the dielectric substrate, so as topenetrate part of the waveguide tube divided into two parts. Therefore,when the dielectric substrate is formed as a ceramic substrate includingalumina or the like, it becomes difficult to machine the dielectricsubstrate. Further, coupling of the micro-strip line is achieved at aposition where the intensity of electric fields generated by a standingwave generated at a terminal end of the waveguide is high. The couplingcharacteristic is determined by the positional relationship between thedielectric substrate including the micro-strip line and the waveguidetube. Therefore, the coupling characteristic is affected by theprecision of assembling the dielectric substrate and the waveguide tube,which makes it difficult to obtain a line-conversion characteristicaccording to a predetermined design without variations.

In the line converter according to Patent Document 2, the dielectricsubstrate is provided in a predetermined direction that is perpendicularto the electromagnetic-wave propagation direction of the waveguide tube.Therefore, the positional relationship between the three-dimensionalwaveguide formed by the waveguide tube and the plane circuit formed bythe dielectric substrate is determined with a low degree of flexibility.Subsequently, the plane circuit cannot be provided in a predetermineddirection that is parallel to the electromagnetic-wave propagationdirection of the waveguide tube.

SUMMARY OF THE INVENTION

In order to overcome the problems described above, preferred embodimentsof the present invention provide a line converter wherein a planecircuit can be arranged in a predetermined direction that issubstantially parallel to the direction in which an electromagnetic wavepropagates through a three-dimensional waveguide, a dielectric substratecan be easily machined, and the characteristic of coupling between theplane circuit provided on the dielectric substrate and thethree-dimensional waveguide is prevented from being affected by theprecision of assembling the plane circuit and the three-dimensionalwaveguide so that a line-conversion characteristic according to apredetermined design can be easily obtained. The preferred embodimentsof the present invention also provide a high-frequency module includingsuch a unique line converter, and a communication device.

According to a preferred embodiment of the present invention, a lineconverter includes a three-dimensional waveguide for propagating anelectromagnetic wave in a three-dimensional space and a plane circuithaving a predetermined conductor pattern disposed on a dielectricsubstrate, so as to perform line conversion between the plane circuitand the three-dimensional waveguide.

The line converter is characterized in that the dielectric substrate isarranged so as to be substantially parallel to a plane E of thethree-dimensional waveguide and at an approximately central portion ofthe three-dimensional waveguide, and the conductor pattern of thedielectric substrate includes a conductor portion defining a shield areaof the three-dimensional waveguide, a coupling-line portion that iselectromagnetically coupled to a standing wave that occurs in the shieldarea, and a transmission-line portion continuing from the coupling-lineportion.

Thus, a standing wave required for electromagnetically coupling thethree-dimensional waveguide to the transmission line on the planecircuit is generated by the shield area defined by the conductor portionprovided on the dielectric substrate. Therefore, the positionalrelationship between the conductor portion on the dielectric-substrateside defining the shield area of the three-dimensional waveguide and thecoupling-line portion that is electromagnetically-coupled to thestanding wave generated at the shield area is determined only by theprecision of forming the conductor pattern on the dielectric substrate.Subsequently, a stable coupling characteristic can be obtained withoutbeing affected by the precision of assembling the three-dimensionalwaveguide and the plane circuit, and a line-conversion characteristicaccording to a predetermined design can be obtained.

Further, preferred embodiments of the present invention are alsocharacterized in that the conductor portion defining the shield areaincludes ground conductors disposed on both surfaces of the dielectricsubstrate.

Further, preferred embodiments of the present invention are additionallycharacterized by having a plurality of conduction paths that penetratesthe dielectric substrate and that is aligned on at least one of bothsides thereof, so as to be spaced away from the transmission line by asmuch as a predetermined distance, so that conduction is establishedbetween the ground conductors located on the both surfaces of thedielectric substrate.

Further, additional preferred embodiments of the present invention arecharacterized in that a conductor of the three-dimensional waveguide isdivided into two portions including an upper portion and a lower portionby a plane that is substantially parallel to the E plane and a space isprovided in the conductor of the three-dimensional waveguide, so as tocreate a choke defined by the space, where the space is provided at aposition spaced away from the three-dimensional waveguide by as much asa predetermined distance, so as to be substantially parallel to anelectromagnetic-wave propagation direction of the three-dimensionalwaveguide.

Further, other preferred embodiments of the present invention arecharacterized by including the line converter and a high-frequencycircuit connected to each of the plane circuit and the three-dimensionalwaveguide of the line converter.

Further, according to another preferred embodiment of the presentinvention, a communication device includes the high-frequency module ina unit for transmitting and receiving an electromagnetic wave.

Other features, elements, steps, characteristics and advantages of thepresent invention will become more apparent from the following detaileddescription of preferred embodiments thereof with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(A)-1(C) show sectional views and a plan view of a line converteraccording to a first preferred embodiment of the present invention.

FIGS. 2(A)-2(D) show exploded plan views illustrating the lineconverter.

FIG. 3 is a sectional view showing an example electric-field intensitydistribution of a three-dimensional waveguide illustrating the result ofthree-dimensional electromagnetic-field analysis simulation for the lineconverter.

FIG. 4 is a plan view showing the result of three-dimensionalelectromagnetic-field analysis simulation for the line converter.

FIG. 5 is another plan view showing the result of three-dimensionalelectromagnetic-field analysis simulation for the line converter.

FIGS. 6(A)-6(C) illustrate a line converter according to a secondpreferred embodiment of the present invention.

FIGS. 7(A)-7(D) show exploded plan views of the line converter.

FIG. 8 is a block diagram illustrating a high-frequency module accordingto a third preferred embodiment of the present invention.

FIG. 9 is a block diagram illustrating a communication device accordingto a fourth preferred embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The configuration of a line converter according to a first preferredembodiment of the present invention will now be described with referenceto FIGS. 1 to 5.

FIG. 1 shows the configuration of the line converter. FIG. 1(C) is aplan view showing the line converter after an upper conductor plate 2and an upper dielectric strip 7 are removed therefrom. FIG. 1(A) is asectional view along line A-A′ of the line converter shown in FIG. 1(C),where the upper conductor plate 2 is mounted thereon. FIG. 1(B) is asectional view along line B-B′ of the line converter shown in FIG. 1(C),where the upper conductor plate 2 is mounted thereon, as in the case ofFIG. 1(A).

Here, reference numeral 1 denotes a lower conductor plate, referencenumeral 2 denotes the upper conductor plate, reference numeral 3 denotesa dielectric substrate, and reference numerals 6 and 7 denote dielectricstrips. The dielectric substrate 3 is arranged so as to be sandwichedbetween the lower conductor plate 1 and the upper conductor plate 2, andthe dielectric strips 6 and 7.

FIG. 2 shows exploded plan views illustrating the configuration of eachportion of the line converter shown in FIG. 1. FIG. 2(A) shows the topsurface of the upper conductor plate 2, FIG. 2(B) shows the top surfaceof the dielectric substrate 3, FIG. 2(C) shows a conductor pattern onthe undersurface of the dielectric substrate 3, and FIG. 2(D) is a planview of the lower conductor plate 1.

A three-dimensional-waveguide groove G11 is provided on the lowerconductor plate 1 (FIG. 2(D)) and a three-dimensional-waveguide grooveG21 is provided on the upper conductor plate 2. The lower dielectricstrip 6 is inserted in the three-dimensional-waveguide groove G11 (FIG.2(D)). The upper dielectric strip 7 is inserted in thethree-dimensional-waveguide groove G21 (FIG. 2(A)). By overlaying thetwo conductor plates 1 and 2 one another, the two dielectric strips 6and 7 are opposed to each other. Subsequently, a dielectric-filledwaveguide (DFWG) (hereinafter simply referred to as a “waveguide”) isformed.

A predetermined plane of the waveguide is determined to be an E plane (aconductor plane that is substantially parallel to the electric field ofa TE10 mode that is the mode of a propagating electromagnetic wave),where the E plane is substantially parallel to the lower conductor plate1 and the upper conductor plate 2. Therefore, the dielectric substrate 3is provided at a position that is substantially parallel to the plane Eof the waveguide and corresponding to the approximately central portionof the waveguide (the portion located between the lower conductor plate1 and the upper conductor plate 2).

The conductor plates 1 and 2 are preferably formed by machining a metalplate including aluminum or other suitable material, for example.Further, the dielectric strips 6 and 7 are preferably formed byinjection-molding or machining a fluoroplastic resin, for example. Thedielectric substrate 3 is preferably formed by using a ceramic substrateincluding aluminum or other suitable material.

A transmission-line conductor 4 a and a coupling-line conductor 4 kcontinuing therefrom are provided on the undersurface of the dielectricsubstrate 3 (the side facing the lower conductor plate 1) (FIG. 2(C)). Aground conductor 5 g is disposed on the top surface of the dielectricsubstrate 3 (the side facing the upper conductor plate 2) (FIG. 2(B)).The transmission-line conductor 4 a located on the dielectric substrate3 and the ground conductor 5 g located on the surface facing thetransmission-line conductor 4 a define a micro-strip line.

A notch portion is provided in the ground conductor 5 g on the topsurface of the dielectric substrate 3, as indicated by referencecharacter N shown in FIG. 2(B). The coupling-line conductor 4 k facingthe notch portion N, the dielectric substrate 3, the lower conductorplate 1, and the upper conductor plate 2 define a suspended line. Thetransmission-line conductor 4 a and the coupling-line conductor 4 k aredisposed on the undersurface-side of the dielectric substrate 3 and theground conductor 4 g (FIG. 2(C)) is located in a predetermined area thatis spaced away from the transmission lines by as much as a predetermineddistance.

As shown in FIG. 2(D), the lower conductor plate 1 has atransmission-line groove G12 that is formed thereon and extends alongthe transmission line 4 a. The transmission-line groove G12 provides apredetermined space on the hotline side of the micro-strip line andfunctions as a shield.

Further, a plurality of conduction paths (via holes) V for achievingcontinuity between the ground conductors 4 g and 5 g on the top surfaceand the undersurface of the dielectric substrate 3 is aligned on bothsides of the transmission-line conductor 4 a and the coupling-lineconductor 4 k, so as to be spaced away therefrom by as much as apredetermined distance. Subsequently, unnecessary coupling between aspurious mode such as a parallel-flat-plate mode generated betweenparallel flat plates, that is, the upper and lower ground conductors 4 gand 5 g sandwiching the dielectric substrate 3 therebetween and amicro-strip-line mode generated by the transmission-line conductor 4 aand the ground conductor 5 g is shielded. Further, unnecessary couplingbetween a suspended-line mode generated by the coupling-line conductor 4k, the dielectric substrate 3, and the conductor plates 1 and 2 and thespurious mode is shielded. Further, the conduction paths (via holes) Vmay be aligned on one side of the transmission-line conductor 4 a andthe coupling-line conductor 4 k, so as to be spaced away therefrom by asmuch as a predetermined distance.

For sandwiching the dielectric substrate 3 having various conductorpatterns disposed thereon between the two conductor plates 1 and 2 inthe above-described manner, the dielectric substrate 3 is provided at apredetermined position with respect to the conductor plates 1 and 2 sothat the coupling-line conductor 4 k is inserted in the waveguide in apredetermined direction that is substantially perpendicular to theelectromagnetic-propagation direction of the waveguide. The groundconductors 4 g and 5 g are arranged on the dielectric substrate 3 sothat a portion of each of the ground conductors 4 g and 5 g is insertedin the waveguide. As shown in FIG. 1, a portion of the ground conductors4 g and 5 g is designated by reference character S. This portion definesa shield area of the waveguide. That is to say, by arranging a groundconductor substantially parallel to the E plane at the approximatelycentral portion of the waveguide, the waveguide is divided by the planethat is substantially parallel to the E plane, whereby the shieldwavelength of the waveguide is reduced and the shield area is located inthe waveguide. Specifically, the portion designated by referencecharacter S functions as a conductor portion defining the shield areaincluded in preferred embodiments of the present invention.

As shown in FIG. 2(A), the upper conductor plate 2 has a choke grooveG22 that is substantially parallel to the electromagnetic-wavepropagation direction of the waveguide and that is spaced away from thewaveguide (from the three-dimensional-waveguide groove G21) by as muchas a predetermined distance. Therefore, where the conductor plate 1 isplaced on the upper conductor plate 2, a clearance generated at theinterface defines a discontinuity portion. However, an electromagneticwave that is likely to leak from the clearance is released in the spaceof the choke groove G22. Where the distance between a portion indicatedby reference characters Co and a portion indicated by referencecharacters Cs corresponds to substantially one-fourth of a propagationwavelength in FIG. 1(B), the portion Co functions as an open end.Subsequently, the portion Cs equivalently functions, as a short-circuitend. Therefore, the radiation loss generated from the clearance createdby the two conductor plates 1 and 2 placed on one another hardly occurs.

The positional relationship between the conductor portion S defining theshield area and the coupling-line conductor 4 k depends on thedimensional precision of the conductor pattern with reference to thedielectric substrate 3. The forming precision of the conductor patternwith reference to the dielectric substrate is significantly higher thanthe assembly precision of the dielectric substrate 3 with reference tothe conductors 1 and 2. Therefore, the relative position of a standingwave of the three-dimensional waveguide, where the standing wave occursby the shield area, with respect to the coupling-line conductor 4 k ismaintained according to a predetermined design at all times.Subsequently, the characteristic of line-conversion between thewaveguide and the plane circuit can be obtained according to thepredetermined design at all times.

Next, the result of simulation performed for an example design will nowbe described according to FIGS. 3 to 5.

The design circumstances are as follows, for example:

Frequency: 76-GHz band

Width of the three-dimensional waveguide grooves G11 and G21(FIG. 1(C)):Wg=about 1.2 mm

Depth of the three-dimensional waveguide grooves G11 and G21 (FIG.1(A)): Hg=about 0.9 mm

Dielectric constant of the dielectric strips 6 and 7: 2

Width of the dielectric strips 6 and 7(FIG. 1(C)): Wd=about 1.1 mm

Height of the dielectric strips 6 and 7(FIG. 1(A)): Hd=about 0.9 mm

Dielectric constant of the dielectric substrate 3(FIGS. 2(B) and 2(C)):10

Thickness of the dielectric substrate 3(FIGS. 2(B) and 2(C)): t=about0.2 mm

Line width of the transmission-line conductor 4 a and the coupling-lineconductor 4 k(FIG. 2(C)): Wc=about 0.2 mm

FIG. 3 shows the result of three-dimensional electromagnetic-fieldanalysis simulation illustrating line conversion between the waveguideand the plane circuit. Further, FIG. 4 shows a cross-sectional view ofthe waveguide portion. In FIG. 3, white and periodically shown patternsindicate the electric-field intensity distribution. In FIG. 4, ring-likepatterns indicate the electric-field-intensity distribution. Whencomparing FIGS. 3, 4, 1(A), and 1(C) to one another, it is clear thatthe standing wave is generated by the waveguide-shield area defined bythe conductor portion S and electromagnetically coupled to the suspendedline defined by the coupled-connection conductor 4 k at a position wherethe electric-field intensity of the standing wave increases to a maximumvalue. That is to say, a distance Ld (FIG. 4) between the conductorportion S defining the shield area and the coupling-line conductor 4 kis determined so that the coupling-line conductor 4 k is provided at apredetermined position where the electric-field distribution of thestanding wave has a maximum value.

The generation of the above-described standing wave is affected by thepositions of ends of the dielectric strips 6 and 7. Therefore, thedistance between the ends of the dielectric strips 6 and 7, and thecoupling-line conductor 4 k is determined so that the coupling-lineconductor 4 k is provided at a position where theelectric-field-intensity distribution of the standing wave has themaximum value. However, variations in the distance between the ends ofthe dielectric strips 6 and 7, and the coupling-line conductor 4 k exerta relatively small influence on the standing-wave generation. Therefore,the assembly precision of the dielectric strips 6 and 7, and thedielectric substrate 3 with reference to the conductor plates 1 and 2may be low.

The mode of the above-described suspended line is converted to the modeof the micro-strip line defined by the transmission-line conductor 4 aso that electromagnetic waves are propagated in order.

FIG. 5 shows the result of reflection characteristic S11 in theline-conversion portion. As shown in this drawing, a low-reflectioncharacteristic of under about −40 dB is obtained in a 76-GHz band.Subsequently, it becomes possible to provide a line converter havinghigh line-conversion efficiency.

Next, a line converter according to a second preferred embodiment of thepresent invention will be described with reference to FIGS. 6 and 7.

The line converter according to the second preferred embodiment performsline conversion between a hollow rectangular waveguide tube and a planecircuit. FIG. 6(C) is a plan view of the line converter after an upperconductor plate is removed therefrom. FIG. 6(A) is a right-sideelevational view of the line converter, where the upper conductor plateis mounted thereon, and FIG. 6(B) is a sectional view of a B-B′ portionof the line converter shown in FIG. 6(C), where the upper conductorplate is mounted on the line converter, as in the case of FIG. 6(A).

Here, reference numeral 1 denotes a lower conductor plate, referencenumeral 2 denotes the upper conductor plate, and reference numeral 3denotes a dielectric substrate. The dielectric substrate 3 is arrangedso as to be sandwiched between the lower conductor plate 1 and the upperconductor plate 2.

FIG. 7 shows exploded plan views illustrating the configuration of eachelement and portion of the line converter. FIG. 7(A) shows the topsurface of the upper conductor plate 2, FIG. 7(B) shows the top surfaceof the dielectric substrate 3, FIG. 7(C) shows a conductor pattern onthe undersurface side of the dielectric substrate 3, and FIG. 7(D) is aplan view of the lower conductor plate 1.

A three-dimensional-waveguide groove G11 is provided on the lowerconductor plate 1 (FIG. 7(D)) and a three-dimensional-waveguide grooveG21 is provided on the upper conductor plate 2 (FIG. 7(A)). Byoverlaying the two conductor plates 1 and 2 one another, the twothree-dimensional-waveguide grooves are opposed to each other.Subsequently, the hollow rectangular waveguide tube (hereinafter simplyreferred to as a “waveguide tube”) is formed.

Unlike the first preferred embodiment, the waveguide tube has apass-through configuration in predetermined areas shown in FIGS. 6 and 7so that no dielectric material is filled therein.

A predetermined plane of the waveguide tube is determined to be an Eplane (a conductor plane that is substantially parallel to the electricfield of a TE10 mode that is the mode of a propagating electromagneticwave), where the E plane is substantially parallel to the lowerconductor plate 1 and the upper conductor plate 2. Therefore, thedielectric substrate 3 is provided at a position that is substantiallyparallel to the E plane of the waveguide tube and that corresponds tothe approximately central portion of the waveguide tube (a portionbetween the lower conductor plate 1 and the upper conductor plate 2).

A transmission-line conductor 4 a and a coupling-line conductor 4 kcontinuing therefrom are disposed on the undersurface of the dielectricsubstrate 3 (the side facing the lower conductor plate 1) (FIG. 7(C)). Aground conductor 5 g is disposed on the top surface of the dielectricsubstrate 3 (the side facing the upper conductor plate 2) (FIG. 7(B)).The transmission-line conductor 4 a disposed on the dielectric substrate3 and the ground conductor 5 g disposed on the plane facing thetransmission-line conductor 4 a define a micro-strip line. In thispreferred embodiment, the ground conductor 5 g is provided only on thetop-surface side of the dielectric substrate 3.

A notch portion is formed in the ground conductor 5 g, as indicated byreference character N shown in FIG. 7(B). The coupling-line conductor 4k facing the notch portion N, the dielectric substrate 3, the lowerconductor plate 1, and the upper conductor plate 2 define a suspendedline.

When the dielectric substrate 3 is sandwiched between the two conductorplates 1 and 2, as is the case with the first preferred embodiment, thedielectric substrate 3 is provided at a predetermined position withreference to the conductor plates 1 and 2 so that the coupling-lineconductor 4 k is inserted in the waveguide in a predetermined directionthat is substantially perpendicular to theelectromagnetic-wave-propagation direction of the waveguide tube. At thesame time, the dielectric substrate 3 is provided at a predeterminedposition so that the ground conductor 5 g is inserted in theapproximately central portion of the waveguide tube, so as to besubstantially parallel to the E plane. A waveguide-shield area of thewaveguide is defined by a predetermined portion designated by referencecharacter S shown in FIG. 6 of the ground conductor 5 g. The portionindicated by reference character S is a conductor portion defining theshield area.

According to the above-described configuration, line conversion betweenthe hollow waveguide tube and the plane circuit can be achieved.

Further, according to the first and second preferred embodiments, thecoupling-line conductor, the transmission-line conductor, and the groundconductors are preferably located on the surfaces of the dielectricsubstrate 3. However, some or all the conductors may be disposed insidethe dielectric substrate (internal layers).

Further, the dielectric-filled waveguide is preferably used in the firstpreferred embodiment, as the three-dimensional waveguide, and the hollowwaveguide tube is preferably used in the second preferred embodiment, asthe three-dimensional waveguide. However, a dielectric line including adielectric strip sandwiched between parallel conductor planes may beformed. Particularly, a non-radiative dielectric line may be formed.

Next, the configuration of a high-frequency module according to a thirdpreferred embodiment will be described with reference to FIG. 8.

FIG. 8 is a block diagram showing the configuration of thehigh-frequency module according to the third preferred embodiment of thepresent invention.

In FIG. 8, reference characters ANT denote a transmission/receptionantenna, reference characters Cir denote a circulator, each of referencecharacters BPFa and BPFb denotes a band-pass filter, each of referencecharacters AMPa and AMPb denotes an amplifier circuit, each of referencecharacters MIXa and MIXb denotes a mixer, reference characters OSCdenote an oscillator, reference characters SYN denote a synthesizer, andreference characters IF denote an intermediate-frequency signal.

The MIXa mixes an input IF signal and a signal output from the SYN, theBPFa makes only a predetermined signal of the mixed output signalstransmitted from the MIXa pass, where the predetermined signalcorresponds to a transmission-frequency band. The AMPa amplifies theelectrical power of the signal and transmits the signal from the ANT viathe Cir. The AMPb amplifies reception signals taken from the Cir. TheBPFb allows only a predetermined signal of the reception signalstransmitted from the AMPb to pass, where the predetermined signalcorresponds to a reception-frequency band. The MIXb mixes a frequencysignal transmitted from the SYN and the reception signal, and outputs anintermediate-frequency signal IF.

A predetermined high-frequency component including the line converteraccording to the first preferred embodiment, or the second preferredembodiment can be used, as the amplifier circuits AMPa and AMPb shown inFIG. 8. That is to say, the dielectric-filled waveguide or the hollowwaveguide is preferably used, as the transmission line, and the planecircuit including an amplifier circuit provided on the dielectricsubstrate is preferably used. By using the high-frequency componentincluding the amplifier circuits and the line converter, ahigh-frequency module with a low loss and good communication performanceis obtained.

Next, the configuration of a communication device according to a fourthpreferred embodiment of the present invention will be described withreference to FIG. 9.

FIG. 9 is a block diagram showing the configuration of the communicationdevice according to the fourth preferred embodiment. The communicationdevice preferably includes the high-frequency module shown in FIG. 8 anda predetermined signal-processing circuit. The signal-processing circuitshown in FIG. 9 includes an encoding-and-decoding circuit, asynchronization-control circuit, a modulator, a demodulator, a CPU, andso forth, and further includes a circuit for inputting and outputtingtransmission and reception signals to and from the signal-processingcircuit. Thus, the communication device including the high-frequencymodule is provided and the high-frequency module is used as a unit fortransmitting and receiving an electromagnetic wave.

Thus, by using the above-described line converter for performing lineconversion between the three-dimensional waveguide and the planecircuit, and the high-frequency module using the line converter, acommunication device with a low loss and good communication performanceis provided.

As has been described above, various preferred embodiments of thepresent invention enable a shield area of a three-dimensional waveguideto be defined by using a conductor pattern of a dielectric substrate.Therefore, the positional relationship between a conductor portion onthe dielectric-substrate side, where the conductor portion defines theshield area of the three-dimensional waveguide, and a coupling-lineportion electromagnetically-coupled to a standing wave generated in theshield area can be determined only by the precision of forming theconductor pattern with reference to the dielectric substrate.

Subsequently, it becomes possible to obtain a stable couplingcharacteristic and a line-conversion characteristic according to apredetermined design, without being affected by the precision ofassembling the three-dimensional waveguide and the plane circuit.

Further, according to various preferred embodiments of the presentinvention, the conductor portion defining the shield area includesground conductors disposed on both surfaces of the dielectric substrate.Therefore, the shielding effect of the three-dimensional waveguideincreases and the size of the line converter decreases.

Further, according to various preferred embodiments of the presentinvention, conduction is established between the ground conductors byusing conduction paths. The conduction paths are formed on at least oneof both sides of the transmission line, so as to be spaced away from thetransmission line by as much as a predetermined distance and on both thesurfaces of the dielectric substrate, so as to be arranged along thetransmission line. Subsequently, the coupling line and the transmissionline are hardly coupled with a spurious mode, so that a good spuriouscharacteristic can be obtained.

Further, according to various preferred embodiments of the presentinvention, a space is provided in the conductor of the three-dimensionalwaveguide, so as to define a choke, where the space is provided at apredetermined distance from the three-dimensional waveguide, so as to besubstantially parallel to the electromagnetic-wave propagation directionof the three-dimensional waveguide. Subsequently, where the twoconductor plates are joined together and the three-dimensional waveguideis provided, the radiated electrical-power loss of the three-dimensionalwaveguide decreases.

Further, other preferred embodiments of the present invention provide alow-loss high-frequency module including a line converter and ahigh-frequency circuit connected to a plane circuit and athree-dimensional waveguide of the line converter.

Further, another preferred embodiment of the present invention providesa communication device with decreased losses caused by line conversionand a suitable communication characteristic.

As has been described, according to the line converter of variouspreferred embodiments of the present invention, the characteristic ofcoupling between the plane circuit and the three-dimensional waveguidethat are provided on the dielectric substrate is not affected by theprecision of assembling the plane circuit and the three-dimensionalwaveguide so that a line-conversion characteristic according to apredetermined design can be easily obtained. Therefore, the lineconverter can be used for a high-frequency module and a communicationdevice used for at least one of a microwave band and a millimeter-waveband, for example.

While the present invention has been described with respect to preferredembodiments, it will be apparent to those skilled in the art that thedisclosed invention may be modified in numerous ways and may assume manyembodiments other than those specifically set out and described above.Accordingly, it is intended by the appended claims to cover allmodifications of the invention which fall within the true spirit andscope of the invention.

1. A line converter comprising: a three-dimensional waveguide arrangedto propagate an electromagnetic wave in a three-dimensional space; adielectric substrate; and a plane circuit having a conductor patterndisposed on said dielectric substrate; wherein the dielectric substrateis arranged to be substantially parallel to an E plane of thethree-dimensional waveguide and at an approximately central portion ofthe three-dimensional waveguide and the conductor pattern of thedielectric substrate includes a conductor portion defining a shield areaof the three-dimensional waveguide, a coupling-line portion that iselectromagnetically coupled to a standing wave that occurs in the shieldarea, and a transmission-line portion extending from the coupling-lineportion.
 2. The line converter according to claim 1, wherein theconductor portion includes ground conductors disposed on two surfaces ofthe dielectric substrate.
 3. The line converter according to claim 2,further comprising a plurality of conduction paths that penetrates thedielectric substrate and that is aligned on at least one of two sides ofthe transmission-line portion, so as to be spaced away from thetransmission line by as much as a predetermined distance, so thatconduction is established between the ground conductors disposed on saidtwo surfaces of the dielectric substrate.
 4. A high-frequency modulecomprising the line converter according to claim 1 and a high-frequencycircuit connected to each of the plane circuit and the three-dimensionalwaveguide of the line converter.
 5. A communication device comprisingthe high-frequency module according to claim 4 provided in a unit fortransmitting and receiving an electromagnetic wave.
 6. The lineconverter according to claim 1, wherein the transmission-line portionincludes a micro-strip line including a ground conductor disposed on oneof the surfaces of the dielectric substrate and a line conductordisposed on the surface opposed thereto and on which the coupling-lineportion is disposed to define a suspended line including the lineconductor disposed on one of the surfaces of the dielectric substrateand the conductor of the three-dimensional waveguide.
 7. Ahigh-frequency module comprising the line converter according to claim 6and a high-frequency circuit connected to each of the plane circuit andthe three-dimensional waveguide of the line converter.
 8. Acommunication device comprising the high-frequency module according toclaim 7 provided in a unit for transmitting and receiving anelectromagnetic wave.
 9. The line converter according to claim 1,wherein a conductor of the three-dimensional waveguide is divided intotwo portions including an upper portion and a lower portion by a planethat is substantially parallel to the E plane and a space is provided inthe conductor of the three-dimensional waveguide so as to create a chokedefined by the space, where the space is provided at a position that isspaced away from the three-dimensional waveguide by as much as apredetermined distance, so as to be substantially parallel to anelectromagnetic-wave propagation direction of the three-dimensionalwaveguide.
 10. A high-frequency module comprising the line converteraccording to claim 9 and a high-frequency circuit connected to each ofthe plane circuit and the three-dimensional waveguide of the lineconverter.
 11. A communication device comprising the high-frequencymodule according to claim 10 provided in a unit for transmitting andreceiving an electromagnetic wave.